Chemical mechanical polishing (CMP) is a process commonly used in the manufacture of high-density integrated circuits to planarize or polish a layer of material deposited on a substrate. A carrier head may provide the substrate retained therein to a polishing station of a CMP system and controllably urge the substrate against a moving polishing pad in the presence of a polishing fluid. Material is removed from the feature side of the substrate that is in contact with the polishing surface through a combination of chemical and mechanical activity. Material removed from the substrate while polishing becomes suspended in the polishing fluid. The suspended material is removed from the polishing station by the polishing fluid.
The carrier head typically includes a retaining ring that circumscribes the substrate and may facilitate holding of the substrate in the carrier head. A bottom surface of the retaining ring is typically in contact with the polishing pad during polishing. The retaining rings may have grooves to promote movement of the polishing fluid to and from the substrate. While polishing a substrate, the slurry and the removed suspended material may adhere and build up in the area between the substrate and the retaining ring. The adhered materials attack the metal surfaces of the retaining ring. Additionally, the adhered material may agglomerate and fall back onto the polishing pad and thus become a source of substrate defect.
Therefore, there is a need for an improved retaining ring, polishing system having an improved retaining ring.